New ultrasound flow modalities for evaluation of congenital heart defects

Recent advances in ultrasound technologies allow the study of cardiac fluid dynamics with higher temporal resolution than ever before. A combination of high frame rate echocardiography (HFRE), obtained by plane-wave imaging, with blood speckle tracking (BST) allows quantification of blood speckle velocities ultimately enabling a direct quantification and visualization of blood flow vorticity, energy loss and intraventricular pressure gradients. The ultrasound group in Trondheim, Norway, has developed a high frame rate echocardiography technique that allows a new approach to blood flow and myocardial function assessment. Two main applications for HFRE are being developed and tested for clinical use in pediatric cardiology: Blood speckle Tracking and mechanical wave imaging (MWI). In this project, we focused mainly on method development, validation and clinical feasibility studies with these techniques. We have during the project period included more than 350 children, performed 30 fetal scans, and 50 animal studies. The method paper describing the feasibility, accuracy and potential clinical applications of BST in pediatric cardiology was just published (Jan 24, 2020). A second paper investigating right ventricular flow dynamics in dilated right ventricles in children is submitted. In this paper vi have investigated and validated energy loss estimation based on BST in volume loaded right ventricles compared to healthy subjects. A new study where we are investigating left ventricular pressure gradients is ongoing, and the first abstract from this data was just submitted. Analysis, validation and feasibility testing of mechanical wave imaging in fetal and animal HFRUS are ongoing, but in an earlier phase. As no good echocardiographic techniques are currently available for the assessment of diastolic function in children, we will utilize a combination inflow hemodynamics assessed by BST with tissue characterization techniques based on MWI to overcome the current limitations. This will be important in our further work, still in collaboration with SickKids Hospital, Toronto, Canada. In September 2019 we sent a first application in a new international pediatric imaging network with focus on HFRUS in the assessment of diastolic function in children. We passed the first evaluation and were invited to send a full application for Foundation Leducq with application deadline February 14th, 2020. Our research was important for the implementation of the qualitative blood speckle imaging technique in clinical available scanners (Vivid E 95, GE Vingmed Ultrasound). The technique “Blood speckle imaging” is based on our research and was launched in 2018. Blood speckle imaging is now available worldwide and implemented in the health care services. However, there is strong need for further development and commercialization of important analysis tools to extract quantitative flow measures. We have today developed an in-house analysis software called PyUSview, which will be further developed and hopefully offered to the international healthcare service soon. This project will continue the next years in the new IN-YOUNG project also founded by samarbeidsorganet. High framerate echocardiography (HFRE) allows a new approach to blood flow and myocardial function assessment, which is ideal for children where the hearts are smaller, depths are limited, and the heartrates are high. Since this technology profits from imaging at shallow depths, the pediatric age group is ideal for the initial trials. In fact, the limitation in penetration depth, gives pediatric imaging an advantage, which has made it possible to develop and offer this diagnostic advance for children first, and not lastly, as for many new medical advances. However, the technique is now also being tested in the adult population. Children with heart disease are very different from adults, and echocardiographic quantitative assessment of cardiac function in children with congenital heart disease is often difficult, sometimes even impossible. The recent development of HFRUS offers novel diagnostic opportunities for resolving these diagnostic challenges. The unique option to measure cardiac blood flow and wall stiffness simultaneously has not been possible previously. This option is highly required by clinicians, and can lead to improved diagnostics and pathophysiologic understanding, which has major impact of the health care of children with cardiac disease. This new diagnostic tool may contribute to generate new markers for prognostic evaluations, which may be of great importance for the patients and their families. The technique “Blood speckle imaging” is based on our research and was launched in 2018. The ultrasound group in department of circulation and medical imaging have a close collaboration with GE Vingmed Ultrasound, to bring new inventions out to the patients as soon as possible. The blood speckle imaging technique is now available bedside in commercially available ultrasound scanners all over the world.